1. Field of the Invention
The present invention relates to a hearing aid for automatically switching to a telephone mode of the type having a first hearing device including a first receiving device for receiving a first input signal, and a second hearing device including a second receiving device for receiving a second input signal. Furthermore, the present invention relates to a corresponding method for automatically switching to a telephone mode.
2. Description of the Prior Art
Modern hearing devices are usually capable of coping with different hearing situations by being able to be switched into different hearing programs by the wearer of the hearing aid. A typical hearing program is the telephone hearing program in which acoustic signals which are picked up by the microphone of the hearing device are filtered in accordance with the frequency spectrum of telephone signals in order to suppress disruptive ambient noises in other spectral ranges.
In addition to one or more microphones, induction receivers which permit a hearing coil mode are provided in hearing devices. This ensures that acoustic signals are transmitted inductively to the hearing device by a telephone device which has an inductively operating loudspeaker. The disruptive sound which is picked up from the surroundings by means of the microphones is then not amplified or transmitted by the hearing device when the wearer makes a phone call.
A problem when switching between the individual hearing programs is the unambiguous detection of a telephone situation. An approach to this is known from PCT application WO 0152597. In this document, the audio signal that is transmitted by the hearing coil is analyzed. If there are signal components which are typical of the telephone mode, the device is switched into the hearing coil mode.
EP 1 298 959 A2 also discloses a method with which the hearing coil signal is analyzed in order to switch automatically into the hearing coil mode or telephone mode. In this context, interference signals which can arise, for example, due to cordless telephones or mobile telephones according to the DECT or GSM transmission standard are used as the basis for a switching signal.
DE 101 46 886 A1 also describes a method with which it is to be possible to detect automatically if the wearer of the hearing aid is making a telephone call. In this methods the signal from the hearing coil and the signal from the microphone of the hearing device are compared with one another and a corresponding switching signal is generated.
The methods described above have the common factor that they are comparatively sensitive to interference.